Selection of perching site background color by Hamadryas feronia (Lepidoptera: Nymphalidae) in Costa Rica: Implications for industrial melanism

Luis Ricardo Murillo-Hiller

doi:10.15517/rbt.v60i3.1774

Abstract

Observations of the increased frequency of melanic forms in moths of the genus Biston in Great Britain after the industrial revolution lead to the development of the theory of Industrial Melanism. Nonetheless, arguments against that interpretation of the experimental evidence have polarized acceptance of the concept. New evidence based on diurnal butterflies is more credible because it involves behavior that can be seen in action, during daylight, and because the natural history of the selected species is well known. An experiment was carried out in which three substrate colors (white, black, and gray) were employed to test the landing preferences of Hamadryas feronia. A marked preference was observed for landing on white and gray, and a chi-square (N=644 tests) showed evidence of a preference by males to land on white, and for females to land on gray. Black was rejected perhaps because it provides very little background matching with the butterfly's colors. The butterfly habit of perching selectively on particular color substrates is a genetically fixed behavior, where the males possibly choose white as a tactic to be noticed by females and attract them, whereas females prefer gray to enhance crypsis and avoid attracting predators.

Highlights

The term camouflage has been used for years even though it generally has been confused with other terms such as disruptive coloration and background matching (Webster et al 2008, Stevens & Merilaita 2009a, Stevens & Merilaita 2009b). Stevens & Merilaita (2009a) proposed that the term camouflage be used to mean all strategies involved in concealment, and Cott (1940) presented circumstantial evidence that concealing coloration plays a major role in secure the safety of otherwise defenseless animals
The goal of this research is to test the color preference of H. feronia butterflies experimentally with regard to their choice of resting sites, to investigate how that relates to their biology and behavior, and perhaps to be able to provide a new example of the industrial melanism concept
A preference for selecting a certain background color to land has been demonstrated in the past for several moth species (Kettlewell 1958a, Sargent 1966, Sargent 1968, Sargent 1969, Steward 1976), in the case of diurnal butterflies very few studies have experimentally proven this conclusion (MongeNájera et al 1998)

Summary

Introduction

The term camouflage has been used for years even though it generally has been confused with other terms such as disruptive coloration and background matching (Webster et al 2008, Stevens & Merilaita 2009a, Stevens & Merilaita 2009b). Stevens & Merilaita (2009a) proposed that the term camouflage be used to mean all strategies involved in concealment, and Cott (1940) presented circumstantial evidence that concealing coloration plays a major role in secure the safety of otherwise defenseless animals. The visual systems of diurnal animals are adapted to permit the detection of distant preys that are best identified by their shapes (Cott 1940, Troscianko et al 2009). Crypsis is a key form of camouflage that initially prevents detection, as disruptive coloration, background matching and masquerade do. Another defense mechanism is for the prey to avoid being caught once it has been detected, for example through motion dazzle (Hanlon et al 2008, Stevens & Merilaita 2009a). The chosen backgrounds consist of small to medium-sized objects of moderate contrast, and for that reason mottled camouflage is extremely common in many animals (Hanlon et al 2008)

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